title: Accuracy and impact of Xpert MTB/RIF for the diagnosis of smear-negative or sputum-scarce tuberculosis using bronchoalveolar lavage fluid.
abstract: BACKGROUND
  The accuracy and impact of new tuberculosis (TB) tests, such as Xpert MTB/RIF, when performed on bronchoalveolar lavage fluid (BALF) obtained from patients with sputum-scarce or smear-negative TB is unclear.
  
  
  METHODS
  South African patients with suspected pulmonary TB (n=160) who were sputum-scarce or smear-negative underwent bronchoscopy. MTB/RIF was performed on uncentrifuged BALF (1 ml) and/or a resuspended pellet of centrifuged BALF (∼10 ml). Time to TB detection and anti-TB treatment initiation were compared between phase one, when MTB/RIF was performed as a research tool, and phase two, when it was used for patient management.
  
  
  RESULTS
  27 of 154 patients with complete data had culture-confirmed TB. Of these, a significantly lower proportion were detected by smear microscopy compared with MTB/RIF (58%, 95% CI 39% to 75% versus 93%, 77% to 98%; p<0.001). Of the 127 patients who were culture negative, 96% (91% to 98%) were MTB/RIF negative. When phase two was compared with phase one, MTB/RIF reduced the median days to TB detection (29 (18-41) to 0 (0-0); p<0.001). However, more patients initiated empirical therapy (absence of a positive test in those commencing treatment) in phase one versus phase two (79% (11/14) versus 28% (10/25); p=0.026). Consequently, there was no detectable difference in the overall proportion of patients initiating treatment (26% (17/67; 17% to 37%) versus 36% (26/73; 26% to 47%); p=0.196) or the days to treatment initiation (10 (1-49) versus 7 (0-21); p=0.330). BALF centrifugation, HIV coinfection and a second MTB/RIF did not result in detectable changes in accuracy.
  
  
  CONCLUSIONS
  MTB/RIF detected TB cases more accurately and more rapidly than smear microscopy and significantly reduced the rate of empirical treatment.
authors.affiliation: Department of Medicine, Lung Infection and Immunity Unit, Division of Pulmonology & UCT Lung Institute, University of Cape Town, , Cape Town, Western Cape, South Africa.
authors.forename: Grant
authors.initials: G
authors.lastname: Theron
authors.forename: Jonny
authors.initials: J
authors.lastname: Peter
authors.forename: Richard
authors.initials: R
authors.lastname: Meldau
authors.forename: Hoosain
authors.initials: H
authors.lastname: Khalfey
authors.forename: Phindile
authors.initials: P
authors.lastname: Gina
authors.forename: Brian
authors.initials: B
authors.lastname: Matinyena
authors.forename: Laura
authors.initials: L
authors.lastname: Lenders
authors.forename: Gregory
authors.initials: G
authors.lastname: Calligaro
authors.forename: Brian
authors.initials: B
authors.lastname: Allwood
authors.forename: Gregory
authors.initials: G
authors.lastname: Symons
authors.forename: Ureshnie
authors.initials: U
authors.lastname: Govender
authors.forename: Mashiko
authors.initials: M
authors.lastname: Setshedi
authors.forename: Keertan
authors.initials: K
authors.lastname: Dheda
mesh_terms: D000328:Adult; D001992:Bronchoalveolar Lavage Fluid / Q000382:microbiology*; D001999:Bronchoscopy; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D009169:Mycobacterium tuberculosis / Q000302:isolation & purification*; D011446:Prospective Studies; D015203:Reproducibility of Results; D013019:South Africa / Q000453:epidemiology; D013183:Sputum / Q000382:microbiology*; D018088:Tuberculosis, Multidrug-Resistant / Q000175:diagnosis*; D014397:Tuberculosis, Pulmonary / Q000175:diagnosis* / Q000453:epidemiology
keywords: Tuberculosis